1. Field of the Invention
This invention relates to an apparatus in which powdered coal put in the carbonizing chamber of a coke oven is controlled to have a homogeneous and optimum packing density.
2. Description of the Prior Art
It has been known both in theory and by experience that the strength of carbonized coke can be improved by increasing the packing density of the coal with which the carbonizing chamber of a coke oven is charged because the distance between the coal particles is decreased with the increase in packing density.
Heretofore, the carbonizing chamber has been charged with coal from above by a natural dumping operation. By this practice, the packing density of the coal mass decreases in an upper part of the chamber while the coal mass in the lower part of the chamber has a high degree of packing density because of the weight of the coal. Such uneven distribution of packing density results in uneven quality of the resultant coke and hinders the improvement in productivity. Particularly, where weakly caked coal is used, such uneven packing density distribution results in coke of low breaking strength. When such coke is charged into a blast furnace as a reducing agent for the production of pig iron, the increased proportion of powdered coke makes it difficult to obtain desired air- and liquid-transmissibility and thus lowers the productivity in the operation of the blast furnace.
The outline of a large scaled industrial coke oven facility is as illustrated in the accompanying drawings of FIGS. 1 and 2. Each carbonizing chamber A in such a coke oven, for example, measures 0.4 to o.5 m in width, 5 to 6 m in height and 14 to 15 m in distance between the back and front sides thereof. On both the front and back sides, there are provided doors 1 and 2. In the upper part of the chamber, there are provided four to five powdered coal charging inlets 3. With each of the carbonizing chambers arranged in this manner, burning chambers are disposed between adjacent carbonizing chambers to form an oven group which includes 80 to 100 chambers arranged in parallel. A powdered coal charging cart C which has a number of powdered coal hoppers corresponding to the powdered coal charging inlets 3 of the carbonizing chamber A is arranged to travel on the upper part of the oven group in the direction of the width of the carbonizing chambers A and thus to charge each carbonizing chamber with the powdered coal up to about 80% of the inside height of each carbonizing chamber A. The powdered coal thus forms an uneven surface 5 with the tips of the protrusions of the uneven surface located immediately below the charging inlets 3 of each chamber while the angle of repose of the powdered coal surface is 36.degree. to 40.degree..
On the rear side of the coke oven group, there is provided a travelling truck F. On the truck F, there are provided a leveler D for leveling off the uneven surface 5 of the charging powdered coal and a pusher E which is arranged for pushing out produced coke from each carbonizing chamber A. The leveler is disposed above the pusher E and levels D off the above stated uneven surface 5 of the charging powdered coal by repeating its movement back and forth from the rear side to the front side and vice versa after each chamber is charged with the powdered coal. This back-and-forth movement of the leveler D is performed for the purpose of securing a passage for a generated gas by leveling the uneven surface of the powdered coal. The accompanying drawing FIG. 3 shows one example of the leveler. In this example, the leveler D is provided with a beam body 8 which has a sufficient length to move in and move out covering the entire length of the carbonizing chamber A and is composed of two side plates 9 and parting strips 10 arranged and suitably spaced between the two side plates 9. Several pairs of guide rollers 11 are arranged to horizontally carry and guide the beam body 8. A driving means 12 is arranged to move the beam body 8 back and forth through a small doorway provided in the upper part of the back door 2 of the carbonizing chamber A. The beam driving means 12 comprises a driving drum 13 disposed on the travelling truck F, front and rear fixed guide sheaves 14, and an endless rope 15 which is wound round these guide sheaves 14. The endless rope 15 is fastened by a clip 16 to the rear part of the beam body 8, so that the beam body 8 can be moved into and out of the carbonizing chamber A over the entire length thereof by causing the driving drum 13 to rotate in the normal and reverse directions. Then the parting strips 10 rake the uneven surface 5 of the powdered coal to effect leveling thereof as the beam body 8 moves back and forth.
The pusher E which is disposed below the leveler D is arranged such that, after coke is produced, the front and back doors 1 and 2 of the carbonizing chamber A are opened, and then the pushing ram 17 of the pusher E is pushed into the carbonizing chamber A to cause the produced coke to be discharged to a quenching cart H through a coke guide cart G disposed on the side of the front door 1.
The arrangement of the coke oven facility is as described in the foregoing. The hardness of the carbonized coke which is obtained from such a coke oven can be improved by increasing the packing density of the charging powdered coal. This has been known both in theory and by experience because the distance between coal particles decreases as the packing density increases. With powdered coal of particle size 3 mm, under 85%, having a water content of 8% used as sample, an experiment has been conducted to see the relation of the packing density in ton/m.sup.3 to various values of heaping depth in m obtained by varying the falling height from the charging inlet. The accompanying drawing FIG. 4 shows the results of the experiment. As shown in FIG. 4(a), the packing density increases as the falling height increases and as the heaping depth increases. The relation of charging depth in m to the cold hardness index DI.sub.15 .sup.150 (%) of coke obtained from a test oven and the relation of the packing density in ton/m.sup.3 to the cold hardness index of the coke DI.sub.15 .sup.150 (%) are as shown in FIGS. 4(b) and (c). As shown, the hardness of the coke produced by the coke oven increases as the packing density of the powdered coal increases.
Heretofore, charging the carbonizing chamber of a coke oven with powdered coal has been carried out by natural dumping from above as mentioned in the foregoing. Then, the packing density of the powdered coal is greater in the lower part of the carbonizing chamber because of a greater falling height and the consolidating action caused by the heaping weight of the powdered coal, and the packing density decreases in the powdered coal located in the upper part of the carbonizing chamber. This uneven packing distribution within the coke oven causes unevenness in the hardness and quality of the coke produced and thus makes improvement in productivity hardly possible. Particularly, when weakly caked coal is used, the breaking strength of the coke obtained therefrom is so low that, when it is used as a reducing agent in a blast furnace, the powderizing rate thereof increases to make air and liquid transmissibility hardly retainable and the productivity of the blast furnace operation becomes too low.